Generally a portable computer, such as a laptop computer, is optimized to reduce size and weight. This often requires tradeoffs, for example, in the size of the display and keyboard, as well as the number and types of ports which are provided in the portable computer.
One way to increase the versatility of a portable computer is to use a docking station. The docking station provides a number of different types of ports for connecting the portable computer to various peripheral devices when the portable computer is docked in the docking station. These ports are used, for example, to drive a large monitor, communicate with various peripherals, such as a keyboard and mouse, provide a connection to a network, and provide connection to an external power supply, such as an AC power source which may be used to charge a battery for the portable computer and provide power for the portable computer when docked.
The docking station may reside in a permanent location with ports connected to the various peripheral devices and an AC power source. For example, when “at the office”, a user can take advantage of the power of a full desktop computer, which is usually not available when a battery is used to provide power for the portable computer, by connecting the portable computer to the docking station. Performance of the portable computer may be scaled back when running on battery power. When the portable computer is docked and connected to the AC power source, the portable computer may be able to increase its performance due to the increased availability of power. Furthermore, when docked, the laptop may be connected to the peripheral devices, such as a keyboard, mouse, and monitor, to substantially function as a desktop computer. When “on the road” the user has the advantage of a light weight and small sized personal computer.
Portable computers, with ever increasing processing speed and capabilities, have incurred some new problems. Portable computers are being equipped with larger and faster processors that dissipate an increasing amount of heat. In addition to processors, other components in the portable computer, such as a power supply, a disk drive, and memory, dissipate a significant amount of heat. In order to maintain an optimum temperature for the components within the portable computer, a cooling system is used to remove the heat dissipated by the components.
FIG. 5 illustrates an example of a typical cooling system in a laptop 500. The laptop 500 may include several internal heat generating components, such as a microprocessor, power supply, memory, etc. For purposes of illustration, only a microprocessor 510 and a power supply 512 are shown. Affixed to the microprocessor 510 and the power supply 512 are evaporators 502 and 504. The evaporators 502 and 504 may include heat sinks, such as an aluminum or copper block or other material with sufficient heat transfer properties, for collecting the heat generated by the components. Attached to the evaporators 502 and 504 are heat pipes 520 and 522. Heat pipes are commonly used to transfer heat from one location to another. Heat pipes are commercially available from companies such as Thermacore. Heat dissipated by the heat generating components and collected at the evaporators 502 and 504 is transferred via the heat pipes to a condenser 530. Air is drawn into the housing 550 through an inlet 540 by a fan (not shown) and across the condenser 530. Heat from the condenser 530 is transferred to the ambient air. The heated air exits the housing 550 at the outlet 542. The condenser 530 may include a finned heat sink to increase the surface area of the condenser 530, thereby increasing the amount of heat transferred to the ambient air.
Laptops are generally performance limited when compared to their desktop counterparts. A laptop with a similar microprocessor and memory is generally configured to consume less power than a similar desktop machine due to the limited availability of power (e.g., limited battery capacity) and the limitations of the cooling system employed by the laptop. As described previously, a portable computer may be scaled back when running on battery power. For example, microprocessor power consumption is generally gated when the laptop is running on battery power. On the other hand, when a laptop is connected to an AC power source, such as when docked in a docking station, the gating mechanism is reduced or de-activated to allow the microprocessor to increase performance, such as increase processing speed. However, even when a laptop is docked in a docking station, the microprocessor may not increase performance to its maximum capacity due to increased heat dissipation and limitations on the laptop cooling system. For example, a secondary effect of running the laptop on AC power is that heat is dissipated in the battery compartment due to inefficiencies in the charging process. Furthermore, when a laptop is docked in a docking station, the laptop is typically closed, causing more heat to remain in the housing of the laptop. The increased heat dissipation when the laptop is docked and the inherent limitations placed on a laptop cooling system, such as size of condensers and evaporators, are limiting factors on the docked performance of a laptop. These limiting factors may result in the performance of the microprocessor being scaled back.